322 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
The pollen-tube, after its entrance into the embryo-sac, increases 
rapidly in diameter, in some cases forming a pouch-like tip. The 
definitive nucleus of the embryo-sac is remarkably large. There is 
evidence of the occasional commencement of the formation of endosperm 
before the fusion of the sexual elements, and even before the entrance of 
the pollen-tube into the embryo-sac. 
Embryogeny of Rosacese and Calycanthacese.* — Dr. B. Longo 
points out a remarkable resemblance in the mode of formation of the 
embryo in these two orders. In all the Rosacea) there are a number of 
equivalent embryo-sac mother-cells ; these mother-cells divide tangen- 
tially, each giving rise to a series of daughter-cells, of which usually 
the innermost enlarge, and may be regarded as so many embryo-sacs. 
Of these embryo-sacs, however, never more than one arrives at a stage 
of differentiation at which impregnation can take place, the others being 
arrested in development. Precisely the same phenomenon was observed; 
by the author in Calycanthus occidentalis and ChimonantJius fragrans. 
Although a plurality of embryo-sac mother-cells is not uncommon, the 
Rosacese and the Calycanthaceae are the only orders at present known in 
which it is constant. 
Embryo and Endosperm in the Parietales.j — Herr E. Pritzel dis- 
cusses this subject at length, especially in connection with the cell- 
contents. Those of the endosperm belong to two types; it contains 
either (1) oil or protein-grains, or (2) starch ; never both of these 
groups of substances. The chemical character of the endosperm is 
constant in large groups. The contents of the embryo, on the other 
hand, vary greatly ; all three groups of reserve-substances, oil, protein,, 
and starch, may be found in company. If there is starch in the endo- 
sperm, there is none in the embryo, while oil and protein-substances 
may occur in both. Starch is present in the embryo only when there is 
no endosperm. The author classifies the orders which make up the 
Parietales under five heads, viz.: — (1) Nutrient tissue copious; embryo 
few-celled, undifferentiated ; (2) Nutrient tissue partially consumed 
before maturity ; embryo somewhat larger ; (3) Nutrient tissue partially 
consumed before maturity ; embryo large, but undifferentiated ; (4) Nu- 
trient tissue partially consumed before maturity ; embryo large, differ- 
entiated into leaf-like cotyledons and radicle ; (5) Nutrient tissue 
completely consumed before maturity ; embryo completely differentiated 
into cotyledons, plumule, and radicle. 
Embryology of Naias and Zannichellia.J — Prof. D. H. Campbell 
describes the origin and development of the sexual elements, the growth 
of the pollen-tube, and the mode of impregnation, in these genera. 
In Naias flexilis the first division of the embryo is transverse, 
dividing it into a basal or suspensor cell, and a terminal or embryo cell. 
The suspensor cell then enlarges considerably, but remains undivided, 
and the whole of the embryo and the secondary suspensor cells are 
* Atti R. Accad. Lincei, vii. (1898) pp. 51-2. 
f Engler’s Bot. Jabrb., xxiv. (1897) pp. 348-94. See Bot. Centralbl., lxxiii. 
(1898) p. 269. 
X Proc. California Acad. Sci., 1897, pp. 1-62 (1 pi.). See Bot. Gazette, xxv. 
(1898) p. 65. 
